1. Field of Invention
The present invention relates to an automatic calibration method for the output power of a pickup head for an optical information recording apparatus. More particularly, it relates to a method that uses curve fitting technology to obtain the correct conversion function between the output current of a front monitor diode and the output power of the pickup head, with which optical information recording apparatuses of the same type can automatically detect the specific power control parameters for corresponding pickup heads thereof.
2. Related Art
Currently, the common write strategy for optical information recording apparatuses adopts the method of multi-pulse/multi-level. The write power is determined by the optimal power calibration (OPC).
The OPC is to first write data on a small segment of an optical disc according to the write strategy and the information prerecorded and then to obtain the corresponding optimal power control parameters, so that the optical information recording apparatus can have the optimal recording characteristics.
The so-called xe2x80x9cmulti-pulse/multi-levelxe2x80x9d is obtained by controlling the ON/OFF timing and power level of each power control channel on the optical information recording apparatus. If the characteristics of each power control channel differ from one another, then the optical information recording apparatus also has different parameters for each respective set of power control channel. Besides, since the characteristics of each laser diode drive and the characteristic of each pickup head vary, the power control channel input parameter for different optical information recording apparatuses will be different from one another too.
To obtain the optimal recording characteristics for every optical information recording apparatus, the power control channel of each optical information recording apparatus should have corresponding specific power control parameters in principle. To obtain these specific power control parameters, the characteristics of each pickup head has to be calibrated after finishing the optical information recording apparatus installation. This inevitably increases the trouble in mass-producing optical information recording apparatuses.
A conventional method of solving this problem is to select an average of the relationship between the output power and the input specific power control parameters from statistical viewpoint. Although this cannot ensure that each pickup head obtains the optimal recording characteristics, the specific power control parameters thus found is not very far from the optimal one.
To obtain the optimal recording characteristics for every optical information recording apparatus, each set of power control channel of each optical information recording apparatus should have corresponding specific power control parameters in principle. To obtain these specific power control parameters, the characteristics of each pickup head has to be calibrated after finishing the optical information recording apparatus installation.
It is a primary object of the present invention to provide an automatic calibration method for the output power of a pickup head for an optical information recording apparatus, which prevents the disturbance of individual pickup head characteristics measurement during the manufacturing processes. In particular, it enables each optical information recording apparatus to automatically measure the specific power control parameters of each set of power control channel so as to obtain the optimal recording characteristics.
The automatic calibration method for the output power of a pickup head for an optical information recording apparatus avoids laser diode temperature rising effects using duty cycle control and obtains the correct conversion function between the output current of a front monitor diode and the output power of the pickup head by curve fitting. This method only needs to measure one set of front monitor diode output current and output power conversion function of the pickup head. The same conversion function is applicable to all pickup heads of the same type. The optical information recording apparatus automatically detects the corresponding parameter for the pickup head. Each optical information recording apparatus can also automatically detect the specific power control parameters for each set of power control channel to obtain the optimal recording characteristicss.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art from this detailed description.